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Conférence : Triterpènes Issus Du Latex Des Euphorbes Cactoïdes Marocaines: Obtention, Réactivité Et Activités Biologiques

Pr. Ahmed Benharref

Laboratoire de Chimie Biomoléculaire, Substances Naturelles et Réactivité, URAC 16, Faculté des Sciences Semlalia, Université Cadi Ayyad, Marrakech, Morocco

Le 05 Apr 2018 à 11:15
Salle des Thèses

Conférence : A venir

Claudia Fuenteaba

Escuela de Alimentos Pontificia Universidad Católica de Valparaíso Waddington 716, Playa Ancha, Valparaíso Chili

Le 12 Apr 2018 à 11:00
Salle des thèses

Actualités et Publications

Water-mediated synthesis of disubstituted 5-aminopyrimidines from vinyl azides under microwave irradiation,

Dehbi, O.; Ishak, E. A.; Bakht, M. A.; Geesi, M. H.; Alshammari, M. B.; Chagnault, V.; Kaiba, A.; Lazar, S.; Riadi, Y.

Green Chemistry Letters and Reviews 2018, 11, 62-66.

An efficient and ecofriendly method for the synthesis of disubstituted 5-aminopyrimidines from vinyl azides and urea or thiourea was developed. This reaction proceeds under microwave irradiation conditions in the presence of water as a solvent. The remarkable features of this new protocol are high conversion, short reaction times, cleaner reaction profiles and straightforward procedure.

New iodide-based amino acid molecules for more sustainable electrolytes in dye-sensitized solar cells,

Sagaidak, I.; Huertas, G.; NguyenVan Nhien, a.; Sauvage, F.

Green Chem. 2018.

The electrolyte is the second key component governing at once power conversion performances and stability of dye-sensitized solar cells. Towards the integration of more sustainable materials, we focused in the replacement of the major constituent of the electrolyte, namely the 1,3 di-alkyl imidazolium iodide. We synthesized two new iodide molecules derived from natural amino acid family (L-proline): (S)-2-(methoxycarbonyl)-1,1-dimethylpyrrolidinium iodide (PMeI) and (S)-2-(ethoxycarbonyl)-1,1-ethylpyrrolidinium iodide (PEtI). In combination with the C106 polypyridyl ruthenium(+II) sensitizer, power conversion efficiencies of 7.1% for PMeI and 6.5% for PEtI were obtained under standard Air Mass 1.5G conditions in conjunction with low-volatile 3-methoxypropionitrile-based solvent. The relationship between these new iodide molecules, the power conversion efficiency and interfacial charge transfer processes is herein discussed and systematically compared to the best standard 1,3 di-methylimidazolium iodide.

Gold Catalysis and Photoactivation: A Fast and Selective Procedure for the Oxidation of Free Sugars,

Omri, M.; Sauvage, F.; Busby, Y.; Becuwe, M.; Pourceau, G.; Wadouachi, A.

ACS Catalysis 2018, 1635-1639.

A fast and efficient methodology for the selective oxidation of sugars into corresponding sodium aldonates is herein reported. Hydrogen peroxide was used as a cheap oxidant and electron scavenger, in the presence of only 0.003-0.006 mol % of gold in basic conditions. Three photocatalysts were studied, namely Au/Al2O3, Au/TiO2 and Au/CeO2, the latter being the most efficient (TOF > 750 000 h-1) and perfectly selective. Only 10 minutes exposition under standard incident sunlight irradiation (A.M.1.5G conditions - 100 mW/cm2) affords total conversion of glucose into the corresponding sodium gluconate. Demonstrating its versatility, this methodology was successfully applied to a variety of oligosaccharides leading to the corresponding aldonates in quantitative yield and high purity (>95%) without any purification step. The photocatalyst was recovered by simple filtration and re-used 5 times leading to the same conversion and selectivity after 10 min of illumination.

Revealing cooperative binding of polycationic cyclodextrins with DNA oligomers by capillary electrophoresis coupled to mass spectrometry,

Przybylski, C.; Benito, J. M.; Bonnet, V.; Mellet, C. O.; García Fernández, J. M.

Anal. Chim. Acta 2018, 1002, 70-81.

Gene delivery is critical for the development of nucleic acid-based therapies against a range of severe diseases. The conception of non-viral (semi)synthetic vectors with low cytotoxicity and virus-like efficiency is gathering a lot of efforts, but it represents a fantastic challenge still far from accomplishment. Carbohydrate-based scaffolds offer interesting features towards this end, such as easy availability, relatively cheap cost, tuning properties and a good biocompatibility. The lack of analytical methods providing quantitative and qualitative data on their binding properties with oligonucleotides (DNA/RNA), with a minimal time and sample consumption, represents a limitation for these channels. Here, we attempted to fill the gap by hyphenation of capillary electrophoresis with mass spectrometry (CE-MS). This coupling strategy allows discriminating free and complexed DNA oligomers with cationic cyclodextrins (CDs), determining the stoichiometry where the highest observed is always DNAn: n/3(CD), and unambiguously assigning the partners through m/z detection. Very reliable data were obtained with migration time within 5.5 (standard deviation < 0.5%) and 25 min (standard deviation < 1.1%) for UV and MS detection, respectively. Furthermore, varying the nitrogen/phosphorus ratio (N/P), key parameters relating to the thermodynamics e.g. the micro and macroscopic dissociation constants Kd and KD, respectively (both in low μM range) and the Gibbs free energy ΔG (−16.3 to −26.9 kJ mol−1), and also the cooperativity as Hill number (nH between 0.98 and 15.75) of the supramolecular process can be delineated, providing a unique tool for the high throughput screening and selection of efficient gene delivery carriers.

Physico-chemical studies of resveratrol, methyl-jasmonate and cyclodextrin interactions: an approach to resveratrol bioproduction optimization,

Oliva, E.; Mathiron, D.; Bertaut, E.; Landy, D.; Cailleu, D.; Pilard, S.; Clement, C.; Courot, E.; Bonnet, V.; Djedaini-Pilard, F.

RSC Advances 2018, 8, 1528-1538.

trans-Resveratrol (RSV) is a natural phenolic molecule of the stilbene family known for its anti-oxidant properties in the field of nutraceuticals and cosmetics. Its production by grapevine cell suspensions is induced by the addition to the culture medium of elicitor compounds, methyl jasmonate (MeJA) and cyclodextrins (CDs). Physico-chemical studies were performed to understand the mechanism of action of CDs on this bioproduction of RSV. Inclusion complexes of RSV in CDs were first observed and then interactions with MeJA were identified using various analytical techniques such as UV and nuclear magnetic resonance (NMR) spectroscopies, mass spectrometry (MS) and isothermal titration calorimetry (ITC).

Efficient Synthesis of N-Alkyl Polyhydroxylated Pipecolamide Compounds from D-Glucurono-6,3-lactone,

Kaddour, A.; Toumieux, S.; Wadouachi, A.

Synlett 2017, 28, 2174-2178.

N-Alkyl pipecolamides were efficiently synthesized from D-glucurono-6,3-lactone via a key 5-azido N-alkylamide intermediate that can be used as a scaffold for the synthesis of 4-amino and N-sulfonated pipecolamide derivatives.

Impact of iron coordination isomerism on pyoverdine recognition by the FpvA membrane transporter of Pseudomonas aeruginosa,

Bouvier, B.; Cezard, C.

Phys. Chem. Chem. Phys. 2017, 19, 29498-29507.

Pyoverdines, the primary siderophores of Pseudomonas bacteria, scavenge the iron essential to bacterial life in the outside medium and transport it back into the periplasm. Despite their relative simplicity, pyoverdines feature remarkably flexible recognition characteristics whose origins at the atomistic level remain only partially understood: the ability to bind other metals than ferric iron, the capacity of outer membrane transporters to recognize and internalize noncognate pyoverdines from other pseudomonads... One of the less examined factors behind this polymorphic recognition lies in the ability for pyoverdines to bind iron with two distinct chiralities, at the cost of a conformational switch. Herein, we use free energy simulations to study how the stereochemistry of the iron chelating groups influences the structure and dynamics of two common pyoverdines and impacts their recognition by the FpvA membrane transporter of P. aeruginosa. We show that conformational preferences for one metal binding chirality over the other, observed in solution depending on the nature of the pyoverdine, are canceled out by the FpvA transporter, which recognizes both chiralities equally well for both pyoverdines under study. However, FpvA discriminates between pyoverdines by altering the kinetics of stereoisomer interconversion. We present structural causes of this intriguing recognition mechanism and discuss its possible significance in the context of the competitive scavenging of iron.

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